Plate charging circuit for electrophotography



pm] 5, 1955 w. a BIXBY 2,705,675

PLATE CHARGING CIRCUIT FOR ELECTROPHOTOGRAPHY Filed Jan. 12, 1950 2Sheets-Sheet l FIGURE 4 TREE 3 8 LEAF J V FIGURE 5 INVENTOR. Wil liclrnE. Bixby April 5, 1955 -w. E. BIXBY 2,705,675

PLATE'CHARGING CIRCUIT FOR ELECTROPHOTOCRAPHY Filed Jan. 12, 1950 2Sheets-Sheet 2 ,25 25 53 r 5/ zs vfl IF k FIGURE 2 FIGURE 3 INVENTOR.Wil liom E. Blxby United States Patent PLATE CHARGING CIRCUIT FORELECTROPHOTOGRAPHY William E. Bixby, Columbus, Ohio, assignor, by mesneassignments, to The Battelle Development Corporation, Columbus, Ohio, acorporation of Delaware Application January 12, 1950, Serial No. 138,252

1 Claim. (Cl. 95--1.9)

This invention relates to a novel and educational toy and, inparticular, to an interesting and instructive electrophotographic toykit which will be of interest to the amateur experimenter and willprovide a fascinating and educational toy for children. Specifically,this invention relates to a novel electrophotographic toy apparatus andto its associated elements.

Electrophotography is a dry, electrical method of photography. Plateshaving a coating of a photoconductive material are used in the processand possess the advantage of being capable of repeated use. Thesensitizing process is of an electrical nature and the development ofimages is accomplished by dry powder mixtures. Images produced inaccordance with the method are made permanent by the application ofheat.

The device of the present invention provides a combination of elementsfor carrying out the various steps of the electrophotographic process inan entertaining manner, while at the same time providing educational advantages and features.

It is an object of this invention to provide an electrophotographic toydevice.

It 1s another object of this invention to provide anelectrophotographictoy kit having educational merit as well as entertainment value.

It is a further object of this invention to provide a toy which can beused to reproduce images or print by a dry electrical process.

It is a still further object of this invention to provide a new andnovel electrical power circuit for a toy electrophotographic apparatus.

Other objects and advantages of this invention will become more apparentfrom the following detailed description thereof, especially when read inview of the accompanying drawings wherein,-

Figure l is a top view of the toy kit with the hinged cover removed,

Figure 2 is a vertical section view along the line A--A of Figure 1 withthe hinged cover on, showing the arrangement of elements making up a toykit,

Figure 3 is a diagram of the power supply unit and cooperating elementsfor the device,

Figure 4 illustrates a type of developer tray used with the kit,

Figure 5 represents a few of the various designs and copy material whichmay be provided with the toy kit and illustrates the potentialeducational value of the device.

Referring now to the particular embodiment illustrated by the drawings,is the toy kit housing having hinged cover 11 and provided witli"fourmain compartments 13, 14, and 16. The compartment 13 provides forstorage of the various powders and transfer papers used in the operationof the device. Compartment 14 is reserved for the power supply elements,while 15 is the sensitizing compartment which is light shielded andwhich includes a slit along its lower face through which anelectrophotographic plate is inserted for sensitization under thesensitizing wire 18. Compartment 16 encloses an exposing and fixingsource 19 and, when the device is not being used, serves as storagespace for trays 20-20. A transparent plate glass or plastic copy orplate holder 22 is provided over this compartment. The fixing andexposing element is an ordinary electric light bulb. (These elements areshown in Figures 1 and 2.)

Tray 20 is used in either the developing or cleaning process, or both.When not in use the tray may be stored in compartment 16, as shown inFigure 2. Lips 25-25 are provided so as to fit the tray 20 into storageracks formed by ledges 2626 along either side of compartment 16. Stops3030 are provided in the bottom of each tray 20 and these serve toposition and maintain an electrophotographic plate in place during thecleaning and developing processes.

The sensitizing elements of the toy kit are shown in Figure 3 with thepower supply being represented by electrical symbols while themechanical elements are shown in isometric. The power supply utilizes aspark coil 31 to produce the high voltages required to effect coronadischarge. The energy source is composed of three size D (or flashlightsize) dry cells 32. A condenser 33 completes the list of electricalelements used. Mechanical elements in the sensitizing portion of the kitinclude insulator posts 3535, corona discharge wire 18, and serratedmetal tracks 3838. Condenser 33 should be connected in shunt acrosstracks 3838. Also illustrated in the drawing are xerographic plate 40comprising a photoconductive insulating layer on a conductive backing,and a plate holder 39 made of insulating material, which are representedso as to illustrate the relative positions of the elements during thesensitizing (or charging) process. When not in use the plate 40 mayconveniently be stored inside the housing 10, for example immediatelybelow the hinged cover 11.

Other elements represented in the various figures include containers5050 which are filled with developer material 51 or cleaner material 52,as will be more fully discussed later. 53 represents a supply of papersheets which serve as transfer sheets. A recessed electric plug 60 isprovided in the wall of the kit and the necessary electric extensioncord, although not shown, is also provided with the kit. Energy led inthrough plug 60 is used only for lighting the exposure lamp 19.

The designs shown in Figure 5 illustrate only a few of the numeroussubjects which could be included among the toy kit patterns. Asindicated the patterns provided may be suitable for familiarizingyouthful operators with a variety of educational subjects, including, asillustrated, famous men of history, magic squares, geography, famousships, and plant and animal identification. There are innumerable otherpossibilities for designs of an educational nature and all of them, whenused in connection with the electrophotographic toy kit of thisinvention, as hereinafter more fully described, will provide hours ofentertainment and relaxation.

The operation of the toy can be best described and understood inconnection with all the drawings and figures. Preparatory to using thetoy the trays 2020 should be removed from the shelves in section 16 andcontainers 5050 filled with developer material 51 and cleaner material52 should also be set out so as to be conveniently at hand when needed.The extension cord should also be connected, first at the recessedelectric plug and then to a v. power source. Preferably an On-Off switchis provided in the extension line. The exposure lamp need not beswitched on until needed for the exposure step.

Actual operation of the toy begins with the insertion of theelectrophotographic plate 40 through the slit in section 15. The plate40 contacts the serrated track or runway 38-38 as indicated in Figure 3.Plate holder 39 should be used to hold and direct the plate 40 duringthe charging operation. As the plate is inserted further and furtherthrough the slit its travel across the serrated track 38-38 ischaracterized by a vibratory or jumping action wherein the plate rapidlyopens and closes the power supply circuit by alternately contacting andbreaking contact with the metal runways 33-38. The width of the slit inthe face of the toy is adjusted so as to make it impossible to contactthe discharge wire 18 with the electrophotographic plate 40. Referringagain to Figure 3 it is seen that the opening and closing of the circuitthrough the metal runways 38--38 produces a pulsating current throughthe primary coil 45 of spark coil 31, whereupon a voltage is induced insecondary coil 44. By reason of the slow making-quick breaking of thecircuit (which action is brought about by the on-otf switching effect ofthe plate on the serrated runway and by the condenser 33) the voltageinduced in the secondary is of considerable magnitude and effectivelyunidirectional. This secondary voltage is applied, as indicated,directly across the plate 40 and the corona discharge wire 18. Thecorona spray so produced deposits an electric charge uniformly on thesurface of plate 40. Three or four passes of the plate across theserrated strips are usually sufiicient to provide an adequate, andsubstantially uniform charge density on the plate 40.

The electrophotographic plate 40 charged in the manner just described isnext removed from the plate holder 39 and placed, charged side down,over the glass 22, and exposure lamp 19 is turned on for a suitableperiod of timeten seconds ordinarily being sufiicient. It will beunderstood, of course, that during this exposure step a suitable patternor image to be reproduced is positioned between the glass 22 and thecharged electrophotographic plate 40. Numerous samples of these patternsare illustrated in Figure 5, it being understood that the patterns orimages to be reproduced are printed, drawn, or otherwise permanentlyaflixed to a transparent material, so as to permit light to pass throughthe non-image areas. Thus, in accordance with known electrophotographicprinciples, the electrostatic charges on the non-image areas arereleased by reason of the areas becoming electrically conductive due tothe light striking them. An electrostatic image of the pattern to bereproduced is thus prepared on the surface of the electrophotographicplate 40.

The plate bearing such electrostatic image is next placed in the bottomof developer tray 20 with the coated side up. Developer powder 51 fromcontainer 50 is poured into the tray 20 which is then rocked back andforth in such a way as to cause the particles of developer powder topass across the electrostatic-image-bearing plate. It will be found thatthese particles will be attracted and held by the electrostaticelectricity on the coating so as to form a powder image of the design onthe transparent sheet through which the exposure was made.

Once developed, the powder image is transferred to a paper surface (apad of suitable paper sheets is supplied with the toy kit) in thefollowing manner: The paper to which the image is to be transferred isplaced over the powder image on the plate and the assembly inserted intothe slot in compartment 15 as in the sensitizing process, the paperbeing next to the sensitizing wire. When the assembly of paper, image,and plate has been inserted and withdrawn from the slot several times,it will be found that the image has transferred to the paper sheet. Thepaper is peeled from the plate, and the transferred image on the paperis fused to the paper by lighting the exposure light 19 and placing thepaper, image side up, over the exposure bulb 19 whereupon the heat fromthe light source 19 will fuse the powder image to the paper sheet. Anypowder particles which still cling to the plate may be removed byplacing the plate in a cleaning tray 21 (which may be the same tray, 20,which was used for developing the image, but which is preferably aseparate tray) pouring some of the cleaner material from the storagebottle into the tray 21 and passing the cleaner back and forth acrossthe plate as was done with the developer powder in the developingprocess. It will be understood that both the developer powder and thecleaner material are poured from the tray 20 or 21 into the properstorage bottle for storage until the next operation.

While the apparatus is operable in a normally lighted room, the chargedplate should not be exposed to intense illumination, i. e., to a stronglight at short distance, or otherwise the plate will be dischargedprematurely.

It will be appreciated that the particular elements of the toy kitherein described are subject to various design revisions without passingbeyond the scope of this invention.

What is claimed is:

An electrophotographic apparatus comprising an electrophotographicplate, a housing member having a slit therein for admitting saidelectrophotographic plate, a corona discharge element within saidhousing and located with respect to said slit so as to spray electriccharges on an electrophotographic plate inserted through said slit, apower supply comprising a spark coil having a primary coil and asecondary coil, a voltage source in series with the primary coil, acondenser in series with said voltage source and said primary coil, apair of serrated contact elements connected one to each side of saidcondenser, one of said contact elements being also connected to one sideof the secondary coil while the other side of said secondary coil isconnected to the corona discharge element. said serrated contactelements being disposed within the housing and extending rearwardly fromthe slit in said housing and spaced laterally to support anelectrophotographic plate inserted through said slit, whereby anelectrophotographic plate inserted through said slit and moving alongsaid serrated contacts alternately makes and breaks electrical contactthereby opening and closing the power supply circuit.

References Cited in the file of this patent UNITED STATES PATENTS1,097,131 Kitsee May 19, 1914 1,279,823 Balsillie Sept. 24, 19181,835,416 Mathis Dec. 8, 1931 2,000,868 Stowell May 7, 1935 2,137,375Alexander Nov. 22, 1938 2,221,776 Carlson Nov. 19, 1940 2,593,978 CajumiApr. 22, 1952 FOREIGN PATENTS 484,142 France Sept. 7, 1917 444,255France Nov. 28, 1919 776,049 France Jan. 15, 1935 815,944 France July26, v 1937 OTHER REFERENCES Xerography, article in American Photographymagazine, for January 1949, page 41.

